Using Weather Station Data in Education

This morning provided an example of how calm winds and clear sky creates local temperature differences. Notice the red line on the chart below. It is the temperature trace for the past 48 hours. At 8:00 a.m. this morning the temperature abruptly began rising. By 9:00 a.m. the temperature warmed from 30 to 38 degrees F. Why? For the answer scroll down to the next chart.

The chart below traces the wind speed for the past 48 hours. Between 6:00 and 8:10 a.m. this morning the wind speed was calm. Then the wind speed increased to a little more than 2 mph. While winds were calm the air stratified, with colder air near the ground and warmer air above. Once the air began moving warmer air mixed down into the colder air. The mixing raised the average temperature.

Temperatures can easily vary by several degrees in the first 10 to 20 feet above the ground. Frost forms on the grass while temperatures are above freezing a few feet above the ground. Weather forecasters know this. When conditions are right frost advisories are issued even though low temperatures are forecast to remain above freezing 4 to 6 feet above the ground where the temperature is measured.

One more thing: If you look at the temperature chart again you will notice how the temperature rise impacted the relative humidity. As the temperature increased, the relative humidity decreased. This is what we would expect to see because temperature and relative humidity are inversely related. As temperature increases relative humidity decreases. If temperature decreases the relative humidity increases.